Question

Which of the following is shown by Photoelectric effect?
${\text{A}}{\text{.}}$ Wave like behaviour of light
${\text{B}}{\text{.}}$ Particle like behaviour of light
${\text{C}}{\text{.}}$ Both wave like and particle like behaviour
${\text{D}}{\text{.}}$ Neither wave like nor particle like behaviour of light

Answer 1

Hint- Here, we will proceed by explaining the photoelectric effect. We will see how exactly electrons are generated when monochromatic radiation falls on a surface. Through this we will analyse which behaviour of the monochromatic radiation is shown.
Complete step-by-step solution -
When a metal surface is exposed to a monochromatic electromagnetic wave of sufficiently short wavelength (or equivalently, above a threshold frequency), the incident radiation is absorbed and the exposed surface emits electrons. This phenomenon is known as the photoelectric effect. Electrons that are emitted in this process are called photoelectrons.
The target material serves as the anode, which becomes the emitter of photoelectrons when it is illuminated by monochromatic radiation. We call this electrode the photo electrode. Photoelectrons are collected at the cathode, which is kept at a lower potential with respect to the anode. The potential difference between the electrodes can be increased or decreased, or its polarity can be reversed. The electrodes are enclosed in an evacuated glass tube so that photoelectrons do not lose their kinetic energy on collisions with air molecules in the space between electrodes.
When the target material is not exposed to radiation, no current is registered in this circuit because the circuit is broken (note, there is a gap between the electrodes). But when the target material is connected to the negative terminal of a battery and exposed to radiation, a current is registered in this circuit; this current is called the photocurrent. Suppose that we now reverse the potential difference between the electrodes so that the target material now connects with the positive terminal of a battery, and then we slowly increase the voltage. The photocurrent gradually dies out and eventually stops flowing completely at some value of this reversed voltage. The potential difference at which the photocurrent stops flowing is called the stopping potential.
From these features of photoelectric effect, we can say that photoelectric effect shows only particle-like behaviour of light (monochromatic radiation.)
Therefore, option B is correct.

Note- The experiments related to photoelectric effect showed that by increasing the light frequency, the kinetic energy of the photoelectrons is also increased. By increasing the light amplitude, the current developed in the circuit due to photoelectrons also increases. The energy of the photons is given by ${\text{E}} = h\nu$ where $h = 6.626 \times {10^{ - 34}}$ Js known as planck’s constant and $\nu$ denotes the frequency in Hz.